Subclinical hypothyroidism and symptoms of depression: Evidence from the National Health and Nutrition Examination Surveys (NHANES)

Background
Subclinical hypothyroidism has been associated with increased risk for depression, yet the findings remain controversial. It is possible that subclinical hypothyroidism is associated with some, but not all symptoms of depression. We examined symptom-specific associations between depression and subclinical hypothyroidism. Methods
Participants (N = 7683 adults) were from the National Health and Nutrition Examination Surveys of 2007–2008, 2009–2010, and 2011–2012 We included participants who had data on their thyroid profile and depressive symptoms (measured using Patient Health Questionnaire), and excluded those with overt hypothyroidism or hyperthyroidism, and those on thyroid hormone replacement therapy. Logistic regression with sampling weights was used to examine the association between subclinical hypothyroidism and depression symptoms. We also ran sensitivity analysis using different cut-off points for defining subclinical hypothyroidism.
Results
Of all the participants, 208 (2.7%) had subclinical hypothyroidism and of them only six had depression. Subclinical hypothyroidism was not associated with depression (OR = 0.61, 95% CI 0.20–1.87) nor with the specific depression symptoms. Using lower criteria for subclinical hypothyroidism diagnosis resulted in similar findings.
Conclusions
In a nationally representative sample of US adults, we observed no association between subclinical hypothyroidism and overall depression risk or any of the individual symptoms of depression.